1. Field of the Invention
The present invention relates in general to an improvement of deck mechanisms of cassette tape recorders, and more particularly, to a mode changing apparatus of a deck mechanism suitable for use in a compact cassette tape recorder which has a simple construction including only one cam gear and one electrically operated solenoid for permitting the mode changing operation of the cassette tape recorder to be accurately carried out and does not cause overrunning of the tape out of the tape cassette during mode changing operations of the tape recorder. The present invention also relates to a method for mode change using such an apparatus.
2. Description of the Related Art
Conventionally, cassette tape recorders ("tape recorders") are electronic devices for playing back audio and video signals recorded on the tape, preferably magnetic tape, of the tape cassette or recording outside sound and image on the magnetic tape. Conventional tape recorders are generally constructed so as to easily change between modes, such as a stop mode, a play mode, a record mode, a reverse play mode and a reverse record mode. In this respect, it is required to provide mode changing apparatus for the cassette deck, or the deck mechanism of the tape recorder. Otherwise stated, the mode changing apparatus is equipped to the tape recorders in order to selectively play back audio and video signals recorded on A or B recording surface of the tape or record outside sound and image on the A or B recording surface as demanded.
In the known mode changing apparatus, a cam gear, rotating upon reception of driving power from a drive motor, carries out a required mode changing operation in cooperation with a solenoid electrically operated upon reception of electric power from an outside power source. As is well known in the art, the known mode changing apparatus requires a pair of cam gears and a pair of solenoids in order to carry out the mode changing operation. One of the cam gears is adapted for mode changing, but the other is adapted for a switching operation. Also, each of the pair of solenoids is adapted for controlling the operation of each cam gear.
In this respect, the known mode changing apparatus of the tape recorders necessarily has a double structure as a result of a pair of power transmission members for driving, using the driving power of the drive motor, the cam gears and the solenoids and a pair of mode changing members, thereby causing the number of required parts to be increased and its construction to be complex. As a result, the manufacturing cost of the deck mechanism is increased and a recent trend for compactness and thinness of the tape recorders can not be effectively accomplished.
A representative deck mechanism having the above described mode changing apparatus is depicted in FIGS. 1a and 1b. In the mechanism of FIGS. 1a and 1b, the mode changing apparatus includes a main gear 142 and a power transmission gear 143 which are hinged to or rotatably mounted on a main plate 141 and rotate upon reception of drive power outputted from a drive motor (not shown). Here, the driving power of the drive motor is applied to the gears 142 and 143 by way of intermediate means and power transmission means, respectively. In addition, a cam gear 144 is rotatably mounted on the main plate 141 and selectively rotates when it is applied with the driving power of the drive motor through the power transmission gear 143, while a solenoid lever 146 is movably mounted on the main plate 141 in order to rotate in response to the operation of a solenoid 145 and, as a result, cause the cam gear 144 to initially engage with the power transmission gear 143. Under the cam gear 144, an upward and downward moving plate 147 is movably mounted on the main plate 141. This moving plate 147 moves upwards and downwards in accordance with the rotation of the cam gear 144. This moving plate 147 is also restricted in its upward and downward movement within a predetermined restriction range under the control of a movable restriction lever 148 which is also rotatably mounted on the main plate 141 and rotates about its hinged shaft according to the rotation of the cam gear 144. The mode changing apparatus further comprises a plate head lever 149 and a leftward and rightward moving plate 150, the former being elastically mounted on the main plate 141 in order to move along with the upward and downward movement of the moving plate 147 while the latter being mounted on the main plate 141 and moving leftwards and rightwards when the restriction lever 148 rotates. A selection lever 152 is hinged to the main plate 141 and provided at its one end with a movable gear 151 which in turn engages with the main gear 142.
The cam gear 144 is provided with a rack 153, an inner cam 154 and an outer cam 155 which are integrally formed with the gear 144. The rack 153 is formed on the circumferential periphery of the gear 144 with provision of predetermined intervals, the inner cam 154 is formed on the lower surface of the gear 144 in order to permit the upward and downward moving plate 147 to selectively move when the cam gear 144 rotates. The outer cam 155 is formed on the lower surface of the gear 144 in order to make the solenoid lever 146 return to its initial position when the cam gear 144 rotates.
Meanwhile, the upward and downward moving plate 147 is integrally provided at its upper part with a stop bolt 156. In addition, first and second stationary plates 157 and 158 are fixed to a lower part of the moving plate 147 while a longitudinal hole 159 is formed on a middle part of this plate 147. This longitudinal hole 159 movably receives the rotating shaft of the cam gear 144 and, in this respect, upwardly and downwardly guided by the rotating shaft of the gear 144.
The restriction lever 148 is provided with a depression part 160 and a locking shoulder 161. As a result, when the upward and downward moving plate 147 moves in an upward or downward direction, .the second stationary plate 158 of this plate 147 is selectively guided by the depression part 160 or engages with the locking shoulder 161 of the restriction lever 148.
The plate head lever 149 has a hole 162 at a side thereof in order to receive the stop bolt 156 of the upward and downward moving plate 147. Also, at a lower part of plate head lever 147, a spring 163 is provided so as to bias the plate head lever 147 in a given direction.
As depicted in these drawings, an end of the leftward and rightward moving plate 150 is connected to an end of the restriction lever 148 and causes the moving plate 150 to move leftwards or rightwards when the restriction lever 148 rotates and, as a result, a depression part 164 on the other end of the moving plate 150 comes into contact with one end of the selection lever 152 or is separated from the one end of the selection lever 152.
In operation of the deck mechanism having the aforementioned construction, upon selection of a play mode at the state shown in FIG. 1a showing a stop mode of the conventional deck mechanism, the drive motor is applied with outside electric power and rotates. The rotational power, or the driving power, of the drive motor is in turn transmitted to the main gear 142 and the power transmission gear 143, both being rotatably mounted on the main plate 141, by way of the power intermediate means and the power transmission means.
At the same time, the electrically operated solenoid 145 is also applied with the outside electric power, causing the solenoid 145 to push the other end of the solenoid lever 146. As a result, the solenoid lever 146 turns clockwise about its hinged shaft and causes its one end, engaging with the outer cam 155 of the cam gear 144, to slightly push the outer cam 155 so as to make this gear 155 rotate clockwise. At this time, since the rack 153 on the outer periphery of the cam gear 144 engages the power transmission gear 143, the rotation of the power transmission gear 143 causes the cam gear 144 to rotate clockwise.
The inner cam 154 on the lower surface of the cam gear 144 pushes the first stationary plate 157 fixed to the upward and downward moving plate 147 and, in this respect, the moving plate 147 moves downwardly under the condition that its longitudinal hole 159 is guided by the hinged shaft of the cam gear 144. Also, since the stop bolt 156 integrally formed with the moving plate 147 is inserted in the hole 162 of the plate head lever 149, this plate head lever 149 moves downwardly as it is biased by the spring 163 when the moving plate 147 moves downwards.
On the other hand, when the upward and downward moving lever 147 moves downwards as described above, the second stationary plate 158 fixed to the lower part of the moving lever 147 escapes from the depression part 160 of the restriction lever 148 in order to be in turn guided by the inclined surface of the restriction lever 147. Therefore, the second stationary plate 158 is caught by the locking shoulder 161. At this time, the leftward and rightward moving plate 150, connected at its end to the one end of the restriction lever 148, moves leftwards due to the downward movement of the moving lever 147.
The depression part 164 formed on the other end of the moving plate 150 then comes into contact with the one end of the selection lever 152 and, as a result, permits the selection lever 152, which is moved by the rotational power of the movable gear 151 rotating along with the rotation of the main gear 142 with which it engages, to stop its turning operation. Thus, when the play mode is selected, interference of an upper movable gear 167 with first and second driven gears 165 and 166 is prevented because of the connection of the moving plate 150 and the selection lever 152.
FIG. 1b shows the deck mechanism after the mode changing operation from the stop mode to the play mode is accomplished. As depicted in this drawing, the solenoid lever 146 returns to its initial position by the rotational power of the outer cam 155 of the cam gear 144 which continuously rotates at this time. The upward and downward moving lever 147 does not return to its initial position, or the upper position, but maintains its lower position, or the downward moved position, because of its locking state wherein it is caught by the locking shoulder 161 of the restriction lever 148.
Also, since the plate head lever 149 maintains its lower position, it drives a head (not shown). At this state, the rotational power of the main gear 142 is transmitted to a reel (not shown) of the tape cassette, loaded on the deck mechanism, by way of a power transmission member (not shown). Thus, the audio signals recorded on the tape out of the tape cassette are permitted to be played back.
On the other hand, when the stop mode is selected at the state of the aforementioned play mode, the aforementioned mode changing operation of the deck mechanism is reversely carried out. To this case, the leftward and rightward moving plate 150 which has supported the turning operation of the selection lever 152 fully returns to its initial position.
Thus, even when the stop mode is selected, the main gear 142 continues its rotation for a moment because of the intrinsic overrunning of the drive motor. This overrunning of the motor occurs since the motor can not stop just after selection of the stop mode but continues its rotation in a predetermined number of revolutions. The lower movable gear 151 engaging the main gear 142 thus rotates, causing the selection lever 152 to be biased toward the rotational direction of the lower movable gear 151.
In this respect, the upper movable gear 167 rotating together with the lower movable gear 151 causes both the first and second driven gears 165 and 166 to rotate in accordance with the mode changing operation for the play mode or the reverse play mode and, as a result, makes the reel of the tape rotate. Hence, the known mode changing apparatus of the tape recorder causes the tape out of the tape cassette to overrun as much as the predetermined number of revolutions of the reel after the stop mode is selected, thereby having a problem in that when the tape recorder starts its play mode or its reverse play mode, the audio and video signals recorded on a part of the tape which overran due to the revolutions of the reel after the stop mode is selected can not be played back.